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Thursday, September 6, 2012

6m / VHF / UHF New Antenna System Complete !!

It was about time I completed a decent 6m & up antenna installation. There was only one spot on my rooftop where I could install the new setup, with minimum coax length and good height from ground level and other surroundings.
A 4el 50Mhz LFA-LN Innovantenna was purchased mid-summer, together with a TennaMast rotator cage, which was a must and made my life much easier.
Two VHF yagi antennas were available and a terrific idea from my good friend Denis, SV5FRD, came up for discussion and study ... to interlace the two yagis, but with different polarization ... Theory was brought down to paper and related literature was downloaded and studied, only to prove that since the elements and the boom of the two antennas would not be in touch with each other, no side-effect on radiation pattern or performance would be present.
So, beginning last Friday, struggling with hot sun and wind gusts, my installation was complete by late Sunday evening.
Below you may see how it looks now:

Total height from rooftop level to the top of the X-300N V/U vertical is 11m. From top to bottom installed are:
Diamond X-300N V/U vertical
10el VHF yagi by Winkler in horizontal polarization
9el VHF yagi by ECO in vertical polarization
4el 50Mhz LFA-LN Innovantenna
Rotator cage by TennaMast
Alliance HD-73 rotator

The mast and the pylon used were of the same material, 48,1mm outside diameter heavy duty galvanized water steel pipe.

Here are a few more shots of the new installation:

In the middle photo above you may see at the background my Cushcraft A3S HF tribander on the main tower.

All mounting hardware and ropes for guying were purchased by Mastrant. Excellent materials, built to last long enough !! Choice of Mastrant's eye bolts + rope clips + turnbuckles proved to be the best combination.

Below, you may see details of the 4el 50Mhz LFA-LN Innovantenna during construction and testing:

Notice the flat aluminum bar going from the 'hot' feed point to the front part of the boom (provided with antenna). This is, in fact, an antenna balun, providing a DC ground on the boom of the antenna itself, thus significantly reducing interferences and noise floor. Also, notice the thick insulators of the elements, they are a great addition to the antenna value, also. Boom is 3,35m long and tuning was done by moving in-out the side aluminums of the driven loop.
This antenna has tuned better than manufacturer's specs ... it shows 1,1:1 VSWR from 50.000 to 50.400 and at 50.800 it shows a 1,4 to 1,5 max VSWR. Sadly, 6m propagation has been absent here the last few days, so not any on-air tests to check F/B and side-lobe attenuation were done yet. Stay tuned for more info on those, later on...

Below is the test position of the 2m/70cm setup, before raising it up the mast:

All three 2m/70cm antennas were already installed here before, so I really had to deal with salt and rust that they had acquired.
The 'kitchen medicine' did it again ... CaCO3 with white vinegar sprayed on the spots in need, effected in less than 3 hours, after which I was able to clean thoroughly and very easy all contacts and aluminum joints. After that, WD-40 was applied throughout those spots and when that dried up, a dehydrant adhesive tape (purchased in Friedrichshafen 2010) was used to protect the spots. On top of it, a thin layer of black silicone filler was applied and at the end two layers of good quality PVC electrical tape with wire strips was installed.
Using antenna analyzer MFJ-259B with a short coaxial showed that the 2 yagis had been tuned as desired. The 10el Winkler shows no more than 1.6:1 at 146.000 and 1.3:1 at 144.000
The 9el ECO shows no more than 1.7:1 at 146.000 and 1.2:1 at 144.000 (exhibits 1:1 at 145.000 exactly !!). The Diamond X-300N shows some higher SWR at both band's edges, but it is OK around 145.100 and 435.500, so no big worries. Anyway, it had so much salt concetrated around its base, that I didn't think it would tune any more ...

Coaxials used were:

H100 by Belden with Amphenol connectors for the X-300N
RG-213C/U by Belden with Amphenol connectors for the two VHF yagis
RG-213C/MIL (made in Italy) with Schuner connectors for the 50Mhz yagi.

I am really looking forward to extensively test the new antennas. I hope the propagation will help me, too!!

Stathis, SV5DKL

1 comment:

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